By Nicola Jones THE beauty and unique properties of crystals are all down to their rigidly uniform structure, identical units repeated millions upon millions of times in a regular 3D pattern. To get a closer look, researchers have grown, for the first time, what is in effect a one-dimensional crystal—a string of units inside the world’s smallest test tube. The crystals, lines of repeating units just two or three atoms wide, were formed inside carbon nanotubes—minuscule honeycomb sheets of carbon atoms rolled into tubes. “Very, very small crystals can’t exist without our help,